Photochemical method of preparing 4-halo-n-acylamides



United States Patent Ofiice 3,368,953 Patented Feb. 13, 1968 This invention relates to methods and intermediates useful in the production of 'y-lactones.

The method of the invention is based on the discovery that N-acylamides of alkanoic acids can be readily N- halogenated with chlorine or bromine in good yields by treating the N-acylamides with an excess of tertiary alkyl hypochlorites or hypobromites preferably in an alkanol solution, and that the N-halo-N-acylamides of alkanoic acids containing at least four carbon atoms in the aliphatic chain bearing on the acylamide group can be rearranged to the corresponding 4-halo-N-acylamides by irradiation, neat or in an inert solvent such as benzene, toluene, fiuorotrichloromethane (Freon-11) or 1,1,2-trichlorotrifiuoroethane (Freon-113), with actinic light. The acyl group may be any alkyl, aralkyl or aryl carbonyl or sulfonyl group.

The 4-halo-N-acylamides can be converted to the corresponding -lactones by treatment with boiling 10% sulfuric acid or by boiling with a 20% aqueous solution of potassium hydroxide, followed by acidification.

The following examples are illustrative of the principles of the invention:

Example I.N-chloro-N-acetylvaleramide N-chloro-N-acetylvaleramide, a pale yellow oil, 7 (neat) 1730 omf is made in good yield by the addition of 3 g. of t-butyl-hypochlorite to a solution of 2.1 g. of N-acetylvaleramide in methyl alcohol. The reaction mixture is allowed to stand for about 2 /2 hours in the dark at room temperature. It is then diluted with Water and extracted with methylene chloride. The extract is washed with water, dried over sodium sulfate and evaporated under vacuum at room temperature.

Example II.-'y-Valer0lacl0ne Irradiation of the N-chloroimide, neat or in solution in Freon-11, Freon-113, benzene or toluene in a Rayonet chamber reactor (3500 A. lamps) or under a Victor 500- watt mercury vapor lamp for 2.5 hours gives 4-chloro-N- acetylvaleramide. The N-chloroimide may conveniently be irradiated in a quartz flask cooled to about 20 C. by a stream of tap water.

Treatment with boiling 10% sulfuric acid for about /2 hour converts the 4-chloro-N-acetylvaleramide to 'yvalerolactone which can be'extracted from the acid with chloroform.

Example III.N-chlor-N-valerylbenzenesulfonamide N-valerylbenzenesulfonamide (2.46 g.) and t-butyl hypochlorite (3.0 g.) allowed to react as in Example I for four hours give N-chloro-N-valerylbenzenesulfonamide in good yield as a pale yellow oil.

This product can be converted to 4-chloro-N-valerylbenzenesulfonamide by irradiation with actinic light and the 4-chloroamide can be converted to -valerolactone by treatment with boiling 10% sulfuric acid or by boiling with a 20% aqueous solution of potassium hydroxide followed by acidification and heating.

Example I V.N-chl0r0-N-acetylbulyramide and 'y-butyrolaclone In the same manner as in Examples I and II, N-chloro- N-acetylbutyramide, 'y(neat) 1725 cmr 4-chloro-N- acetylbutyramide and 'y-butyrolactone are made from N acetylbutyramide.

Example V.N-chlor0-N-acetyl-4-phenylbutyramide and 4-phenyly-butyr0lact0ne In the same manner as in Examples I and II, N-chloro- N-acetyl-4-phenylbutyramide M.P. 3033 C., 'y(neat) 1725 cmf 4-chloro-4-phenyl-N-acetylbutyramide and 4-phenyl-'y-b=utyrolactone 7(CS 1792 cm." are made from N-acetyl-4-phenylbutyramide.

Example VI. N-bromo-N-acetylvaleramide This compound is prepared as in Example I using t-butylhypobromite instead of t-butylhypochlorite. It is readily rearranged to the 4-bromo-N-acetylvaleramide by the action of actinic light (visible or ultraviolet), and can be converted to 'y-valerolactone as in Example H.

Other gamma-lactones which have been made by the methods of the foregoing examples are 4,4-di methyl-'ybutyrolactone, Y(CS2) 1775 cmr from N-chloro-N- acetyl 4 methylvaleramide', and 'y octanoiclactone 'y(neat) 1775 cmr from N-chloro-N-acetyloctanamide.

Ar0matic substances, such as benzene, naphthalene and triphenylene appear to act as sensitizers of the actinic rearrangement of the N-halogen to the 4-position. Particularly good yields of the 4-halo-N-acylamides are obtained by irradiation of the N-halo-acylamides in benzene or in solvent mixtures containing benzene.

I claim:

1. A method of making 4-halo-N-acylamides of alkanoic acids containing at least four carbon atoms in the aliphatic chain bearing the acylamide group which comprises irradiating the corresponding N-halo-N-acylamide with actinic light.

2. A method of making 4-chloro-N-acylamides or alkanoic acids containing at least four carbon atoms in the aliphatic chain beairng the acylamide group which comprises irradiating the corresponding N-chloro-N-acylamide with ultraviolet light.

3. A method of making 4-halo-N-acetylamides of alkanoic acids containing at least four carbon atoms in the aliphatic chain bearing the acetylamide group which comprises irradiating the corresponding N-halo-N-acetylamide with actinic light.

4. A method of making 4-chloro-N-acetylamides of alkanoic acids containing at least four carbon atoms in the aliphatic chain bearing the acetylamide group which comprises irradiating the corresponding N-chloro-N-acetylamide with ultraviolet light.

References ited UNITED STATES PATENTS 3,038,909 6/1962 Kerwin 204-158 3,278,526 10/1966 Louthan et al. 204158 HOWARD S. WILLIAMS, Primary Examiner. 

1. A METHOD OF MAKING 4-HALO-N-ACYLAMIDES OF ALKANOIC ACIDS CONTAINING AT LEAST FOUR CARBON ATOMS IN THE ALIPHATIC CHAIN BEARING THE ACYLAMIDE GROUP WHICH COMPRISES IRRADIATING THE CORRESPONDING N-HALO-N-ACYLAMIDE WITH ACTINIC LIGHT. 